1. Field of the Invention.
The present invention relates generally to electric switches having two or more stationary terminals and a movable bridging contact, and more specifically to an electric switch of this type having a bridging contact that makes with a surface different from the break surface of the fixed terminals in order to avoid the problem of build-up of contamination on the make surface thereof.
2. Description of the Prior Art.
Rocker type switches in which an elongate bridging contact is positioned to be supported by a central fixed terminal so that an end of the bridging contact can be shifted into engagement with an end of a second fixed terminal are well known in the art. These switches commonly have a rocker type switching mechanism, having a spring loaded insulating plunger therein which slides along the elongate bridging contact across the central fixed terminal forming a fulcrum, so that the spring loaded plunger causes the elongate bridging contact to rock about the central fixed terminal into and out of engagement with the second fixed terminal. In this regard, the electrical connection between the movable contact and the second fixed terminal is a simple butt connection. In this type of butt connection, the terminal break surface is also the terminal make surface. The problem with this construction is that when the electrical connection is broken, an electric arc is generated between the two breaking contact elements, thereby depositing electrical contamination on each of these contact surfaces. After repeated breaks of the electrical contacts, this contamination has built up to such a degree that further positive make and break actions are made across these areas of contamination, rather than the initially smooth terminal areas, thereby resulting in extremely highly concentrated areas of current transfer across the build-up of contamination, further compounding the problem and contributing to the build-up of additional arcing contamination. This problem is, of course, greatly accelerated when the switch is used in high current applications.